Kylo goes into Finn's head and sees so much love and light and hope that it kind of cauterizes the dark side out of him, until he's a sobbing mess and Finn wants to hate him, but he ends up being Finn and comforting him instead, and talking about how he understands that sometimes you think there aren't things you Can come back from, but you have to try anyway. No one else trusts Kylo, but Finn's friendship helps open him up to the light again.